Methods absorbing energy using plastically deformable coil energy absorber

#This disclosure relates to energy management systems for pedestrian safety and vehicle damageability, and especially relates to energy absorber systems that employ plastic deformation.

#Increased importance has been placed on methods for minimizing the amount of injury suffered by a pedestrian when struck by a vehicle. Focus has been on bumper assemblies, headlamps. For bumper assemblies, foam resins have been used for energy absorption. Foam based systems typically have slow loading upon impact resulting in a high displacement. Further, while foams are effective to a sixty or seventy percent compression, beyond that point foams become incompressible such that the impact energy is not fully absorbed. The remaining impact energy is absorbed through deformation of a backup beam and/or vehicle structure. Foams are also temperature sensitive so that displacement and impact absorption behavior changes substantially with temperature. Typically, as temperature is lowered, the foam becomes more rigid, resulting in higher loads to attain displacement. Conversely, as temperature rises, foams become more compliant resulting in higher displacements and possible vehicle damage.

#With respect to headlamps, actually, due to their placement at the front or the corners of the vehicle, the headlamps of the vehicle are one of the locations most contacted by a pedestrian in an impact, or damaged in an impact with another vehicle. Several different designs have been proposed for minimizing pedestrian injury during an impact as well as minimizing damage to headlamps (e.g., headlights). Some of them require significant structural modifications to the headlamp which increase its volume, weight, and/or cost. Others require structural modification to the chassis surrounding the headlamp area.

#Refer now to the drawings, which are exemplary, not limiting, and wherein like elements are numbered alike in several figures.

#FIG. 1 is a side view of an embodiment of a compression coil spring comprising a conical geometry.

#FIG. 2 is a side view of an embodiment of a coil spring comprising a conical geometry, illustrating the change in diameter of the spring.

#Energy management systems comprising plastically deformable compression spring(s) can be used in various components within a vehicle system that can benefit from energy absorption. For example, plastic compression spring(s) can be employed in bumper assemblies, light assemblies (e.g., headlamp assemblies, rearlamp assemblies, interior lighting assemblies, and so forth), dashboard assemblies, hood restraint systems, fender assemblies, roof assemblies, door module assemblies and/or steering wheel assemblies. The plastically deformable compression spring(s) can provide energy absorption, which, under the desired degree of energy for a particular area, becomes plastic deformation. Such systems can enable directed tunability (e.g., stiffness at a specific location in a system, with different stiffness elsewhere), individual replacability (individual springs can be replaceable without requiring replacement of the entire component (e.g., replacement of a spring instead of the bumper assembly), reduced component weight, enable the bumper assemblies to meet or exceed pedestrian safety standards, and enhanced vibration stability of the bumper system.

#In some embodiments, the plastically deformable compression springs can be employed as energy absorbers for automotive bumper assemblies. Such assemblies offer improved pedestrian safety with respect to lower leg model testing, upper leg model testing, and knee acceleration modeling, in addition to a reduced system cost by significantly reducing the mass of the component, e.g., by up to 25%. The reduced mass of the energy absorbers additionally aids in providing higher fuel efficiency by reducing the overall mass of a vehicle. The present system employs a plurality of plastically deformable springs across the bumper of a vehicle. The amount of energy required to compress the springs can be tuned (e.g., chosen), based upon several factors such as the type of vehicle, governmental regulations/requirements, the location along the bumper where the spring is located (i.e., each spring can have the same or different compression characteristics than another spring in the bumper). In other words, the bumper can be customized. For example, the energy absorbers disclosed herein meet the requirements of the lower leg impact phase-2 targets with a 20% safety margin and also meet the requirements of the upper leg impact phase-2 regulations.

#A great advantage of this system is that customization can be attained even without multiple types of tooling or equipment. The general design of every bumper assembly can be similar, e.g., with a fascia (e.g., outermost portion of the bumper assembly), springs, and a backing element (e.g., support structure). The difference between the systems can be the specific springs employed. The springs can also be removably attached, e.g., demountable, (i.e., can be removed and reattached to the element to which they are attached, without damaging said element) to the vehicle (e.g., to the fascia, to a bumper beam, to the body in white (BIW), to the body in black (BIB), bumper beam, a front-end module, a radiator support beam, bumper support brackets, a component projecting from the BIW, a component projecting from the BIB, and combinations comprising at least one of the foregoing), enabling facile replacement of a spent spring e.g., after a collision. For example, the spring(s) can have a threaded portion enabling them to be threaded into the appropriate element of the bumper system which will comprise the corresponding female component with mating internal threads. Other possible attachments include an opening into or through the particular element wherein an end of the coil passes into or through the opening and is retained therein, as well as fasteners described below in relation to fastening to the fascia.